1. Field of the Invention
This invention relates to a new process for polymer fractionation. More particularly, the invention relates to a modified FFF process for the separation of polymers having ultra-high molecular weight which gives faster and higher resolution than possible heretofore for such polymers.
Specifically, the invention provides a new process for high speed separation of ultra-high molecular weight polymers, e.g. polymers having a molecular weight higher than 1.times.10.sup.6, by a hyperlayer field-flow fractionation technique. The new process broadly comprises forcing a carrier fluid containing a small sample of the said ultra-high molecular weight polymer through a thin flow channel, applying a primary externally controlled driving force transversely across the thin dimension of the channel, adjusting the flowrate of the fluid and the field strength governing the primary externally controlled force in relationship to the channel thickness such that at least over part of the molecular weight range the entropic force F.sub.e and the primary driving force F.sub.1 are related by the inequality EQU .vertline.F.sub.e .vertline.&gt;.vertline.F.sub.1 .vertline.
at the accumulation wall of the channel.
2. Prior Art
There is a growing need in industry and health sciences for the separation of polymeric and macromolecular material whose components include various kinds of high molecular weight species including polysaccharides, DNA, synthetic polymers and the like.
Various methods have been proposed but in general, they have been too slow, too low in throughput, too labor intensive, too expensive or have failed to effect the separation with the desired degree of resolution.
Some of the highest resolution techniques disclosed have been those based on field-flow fractionation as disclosed in U.S. Pat. No. 3,449,938 and U.S. Pat. No. 4,147,621, but their operation is relatively slow and difficult for ultra-high molecular weight polymers. Various form of electrophoresis have been used for charged biopolymers, but the separation is slow and the operation inconvenient and labor intensive because electrophoresis is a nonelution technique for which sample collection is difficult. Chromotography has been used widely for low and medium sized molecules but is not particularly suited for the fractionation of ultra-high molecular weight polymers because of adsorption, degradation and sample loss problems.
The prior known methods thus present serious defects in meeting the needs of industry particularly in biotechnology and polymer processing. The increasing competitiveness of industry and the rapid evolution of new technologies is now putting extraordinary demands on analytical separation processes for use in process control and product analysis.
There is thus a rapidly growing need for new separation technology applicable to polymers for which the resolution is high and the separation is fast. In addition, because of the enormous variety of separation needs, the separation process should be preferably based on as large a variety of molecule properties as possible.
It is an object of the invention, therefore, to provide a new and efficient process for the fractionation of high molecular weight polymers. It is a further object to provide a new process for the separation of high molecular weight polymers from fluid media which can be accomplished in a very rapid and efficient manner. It is a further object to provide a new process for high molecular weight polymer fractionation which permits a very high resolution of separation. It is a further object of the invention to provide a fractionation operating as an elution technique in which fractions can be conveniently collected from the eluting stream. It is a further object to provide a new process for fractionation of polymers which is particularly effective with ultra-high molecular weight polymers which can be rigid or flexible. It is a further object to provide a fractionation process which is economical to operate and uses inexpensive equipment. These and other objects will be apparent from the following detailed description thereof.